Holographic total-internal-reflection selector for tunable lasers

A new holographic selector, operating on the basis of total internal reflection, is described. An analysis shows that this selector has a higher angular dispersion than the devices available at present and this is combined with lower losses inside a laser resonator. A method is given for the calculation of the parameters of a selector operating in the range of wavelengths (0.2–1.2μ) emitted from tunable lasers. This selector uses holographic volume phase gratings recorded in dichromated gelatin films whose optical strength is 2–4 J/cm² at λ = 1.06μ for pulses of τ_p = 10 nsec duration. Frequency selection and wideband tuning are reported for a neodymium-glass laser. The width of the spectrum does not exceed 0.7cm^–1 in the spiky regime. Single-frequency emission, tunable in a range exceeding 200cm^–1, can be obtained in the Q -switched regime (switching by a passive shutter).